The present invention relates to a portable device for performing wireless communication with a predetermined communication subject.
Vehicles, such as automobiles, nowadays often incorporate electronic key systems to improve vehicle operation convenience. Such an electronic key system locks and unlocks doors and enables the starting of the engine when a unique ID code transmitted from a portable device, which is carried by a user, is identical to an ID code registered in the vehicle. The portable device has a case for accommodating a circuit board on which various electronic components are mounted and a battery for supplying power to the electronic components on the circuit board.
Japanese Laid-Open Patent Publication No. 2005-235837 describes an example of a case for a portable device. The case of the portable device is formed by a first case part and a second case part, which are fastened to each other. More specifically, the first case part has an open end. A plurality of projections are formed at predetermined intervals along the rim of the first case part at the open end. The second case part also has an open end. A plurality of recesses are formed in the rim of the second case part at the open end in correspondence with the projections of the first case part. The projections are engaged with the recesses to fasten the first and second case parts to each other.
The first case part and the second case part are fastened to each other only by the engagement between the projections and the recesses. Thus, a person other than the user may be able to disassemble the case of the portable device in a relatively simple manner. Such a person may disassemble the case by disengaging the projections of the first case part from the recesses of the second case part in order to remove the circuit board from the case. If the first and second case parts are fastened again to each other after the circuit board is removed, the user would not be aware for a while of tampering with the circuit board.